Diesel truck fuel cost starts with litres used
The annual calculation is kilometres divided by 100, multiplied by L/100 km, multiplied by CAD per litre. For a stated scenario of 25,000 km, 14 L/100 km and CAD 1.80/L, the annual diesel cost is CAD 6,300. These are planning inputs, not a tested consumption figure or current pump-price claim.
Use the same annual distance when comparing gas and diesel. Enter the actual price assumption for each fuel separately. A cheaper litre does not necessarily produce a lower annual cost if consumption differs, and a lower annual fuel cost does not establish lower total ownership cost.
Avoid mixing unloaded and towing fuel records
If you have separate consumption information, calculate towing and non-towing distance separately and add the costs. Keep route, weather, load and tire context with the records. A best tank of unloaded highway driving is not a forecast for a full year of mixed duty.
Natural Resources Canada's ratings search provides model-specific light-duty information. Verify the exact application and units before using a figure. U.S. and Imperial MPG are different; converting either to L/100 km requires the correct gallon definition. A published rating is not a measurement of your loaded trailer combination.
Test whether the fuel difference changes the purchase
Vary distance, consumption and fuel prices to see how robust the comparison is. Then move the annual fuel figures into the wider ownership budget, which also includes financing, maintenance and other costs. If the projected diesel saving is small beside the purchase premium or known repairs, it should not dominate the buying decision.